Jude 1, ”Jude, the servant of Jesus Christ, and brother of James, to them that are sanctified by God the Father, and preserved in Jesus Christ, and called.”

The first part of the salutation, Jude told us who he was. Though his family history would seem important, Jude was a servant of Christ, that was who Jude was, his identity. He was a Christian. I hope the same with you. Jude told the readers who we are as Christians. That is an interesting way to start a letter, he told us who he was, then told us who WE are.
We need that reminder. It is easy to be overwhelmed by even normal circumstances of life, and what a comfort, (and sometimes a rebuke) but always a joy to recall who we are in Christ Jesus. Christians can let the world tell them who they are, we can let our enemies tell us who we are; even let the Devil accuse us and tell us who we are. Praise be to God that He graciously tells us, over and again, who we really are in Jesus Christ the Lord.
Almost like a military leader, Jude warns us, in this letter, against false teachers, and writes words of war to encourage the troops. When false teacher come, we must find refuge and strength in who we are, why we are, and what we are. Jude’s identity is in Christ, and that is who we are. Know who you are on account of Christ. Who you are as God sees you and has made you. Therein lays our strength and confidence.
Jude is giving a war time sermon. He is now addressing the soldiers of Christ. You are in the midst of a great spiritual war. This war has been going on for thousands of years, and now it is about to heat up. Your enemies are many, your enemies are great, and your enemies are powerful. You have no choice whether the war will be fought; the battle rages on. You have no choice of whether you will fight this spiritual war against unseen principalities and powers; you will fight or be overcome. This would look bleak, if it were not for one thing — you are the servants of the Lord of Hosts. Soldiers of Christ, consider who you are. Know who you are, not by your own power, or by who you want to be, but by who you are in the Lord Jesus, and all the benefits he provides his people. You’ve been outfitted with the armor of God and empowered by His heavenly power. Jude reminds believers we are sanctified by the Father, preserved in Christ, and called by the Holy Spirit. Called by the gospel, effectually called by the Spirit, and called to be a saint. We’ve been “drafted” in the army of our Father, following the Captain of our salvation, and follow the Lord as His saints, preserved by His grace and power.